#extension GL_OES_EGL_image_external : require
precision mediump float;
uniform samplerExternalOES sTexture;
varying vec2 vTextureCoord;
void main()
{
     vec2 uv = vTextureCoord.xy;

     if (uv.x <= 1.0 / 3.0) {
         uv.x = uv.x * 3.0;
     }else if (uv.x <= 2.0 / 3.0) {
         uv.x = (uv.x - 1.0 / 3.0) * 3.0;
     }else {
         uv.x = (uv.x - 2.0 / 3.0) * 3.0;
     }
     if (uv.y <= 1.0 / 3.0) {
         uv.y = uv.y * 3.0;
     }else if (uv.y <= 2.0 / 3.0) {
         uv.y = (uv.y - 1.0 / 3.0) * 3.0;
     }else {
         uv.y = (uv.y - 2.0 / 3.0) * 3.0;
     }
     // 获取纹理像素，用于显示
     gl_FragColor = texture2D(sTexture, vec2(uv.x, uv.y));
}